Field of the Invention
The present technique relates to a photoelectric conversion device.
Description of the Related Art
There is a ranging apparatus (distance sensor) using a time of flight (TOF) method. In the TOF method, a target of distance measurement is irradiated with light emitted by a light source, and the light reflected by the target is received. On the basis of the relationship between the speed of light and the time period from the irradiation to the light reception, the distance to the target is calculated. Here, the light that has been emitted by the light source for ranging and reflected by the target is referred to as signal light. The received light includes, in addition to the signal light, light (ambient light) derived from a light source different from the light source for ranging, such as natural light or artificial light. To enhance the ranging accuracy, it is effective to separate the ambient light and the signal light from each other.
Japanese Patent Laid-Open No. 2005-303268 (US Patent Application No. 2007/0103748) discloses a technique of removing a component corresponding to ambient light by an apparatus that performs ranging by using a light detecting element. According to the second embodiment of this publication, the light detecting element includes a first photosensitive unit which has a suitable structure for picking out holes and a second photosensitive unit which has a suitable structure for picking out electrons. The holes generated at the first photosensitive unit are held by a hole holding unit through a gate unit, and the electrons generated at the second photosensitive unit are held by an electron holding unit through the gate unit. The holes held by the hole holding unit and the electrons held by the electron holding unit are recombined by a recombination unit, and the carriers remained after the recombination are picked out as object carriers through an output unit.
Japanese Patent Laid-Open No. 2008-89346 (US Patent Application No. 2008/0079833) discloses a technique of removing noise derived from background light (ambient light) by selectively conducting a plurality of charge-storage sections and a plurality of capacitors to extract a difference component of charge stored in the plurality of charge-storage sections.